OLED Buffer Layer for Electron Injection and Sputtering Protection

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Solution Overview

Problem

Existing organic light emitting diode (OLED) devices face challenges in achieving improved transmittance and luminous efficiency, particularly during the manufacturing process of large-area devices, where damage to organic materials and absorption rates are concerns.

Innovation Solution

Incorporating a buffer layer with specific materials such as oxide, fluoride, or quinolate compounds of alkaline metals or alkaline-earth metals, along with materials like ytterbium, aluminum, or silver, having a work function of 2.6 to 4.5 eV, and a thickness of 30 Å to 400 Å, which also includes a hole injection layer doped with P-type materials, to enhance electron injection and reduce damage during sputtering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a buffer layer with oxide, fluoride, or quinolate compounds of alkaline metals or alkaline-earth metals is used, then luminous efficiency is improved, but device complexity increases

Engineering Contradiction:

Improveluminous efficiencyVSAvoiddevice complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

A buffer layer comprising oxide, fluoride, or quinolate compounds of alkaline metals or alkaline-earth metals is introduced as an intermediary layer between the emission layer and the anode. This buffer layer serves as a mediator that improves electron injection from the anode into the emission layer, thereby enhancing luminous efficiency without requiring fundamental changes to the device structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The buffer layer is constructed using composite materials combining oxide, fluoride, or quinolate compounds of alkaline metals or alkaline-earth metals with additional materials having work functions in the range of 2.6 to 4.5 eV. This composite approach allows optimization of both electron injection and hole blocking functions while maintaining improved luminous efficiency.

Inventive Principle:

Principle #40Composite materials

2Productivity

If sputtering is used for anode manufacturing, then productivity is improved, but damage to organic materials increases

Engineering Contradiction:

ImproveproductivityVSAvoiddamage to organic materials

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The buffer layer is deposited beforehand on the anode before the organic emission layers are formed. This pre-deposited buffer layer acts as a protective cushion that prevents direct contact between the sputtering process and the organic materials, thereby reducing sputtering-induced damage while allowing the use of productive sputtering manufacturing methods.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Loss of energy

If the buffer layer thickness is increased, then luminous efficiency is improved, but light transmittance decreases

Engineering Contradiction:

Improveluminous efficiencyVSAvoidlight transmittance

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The thickness of the buffer layer is precisely controlled within the range of 30 to 400 Å. This parameter optimization ensures that the buffer layer is thick enough to provide sufficient electron injection enhancement and hole blocking function for improved luminous efficiency, while remaining thin enough to maintain adequate light transmittance for top-emitting OLED performance.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution results in improved luminous efficiency, driving characteristics, and reduced light absorption, leading to higher transmittance and better performance in large-area OLED devices.

Implementation Method 1

a buffer layer positioned between the emission layer and the anode. The buffer layer comprises a first material including an oxide, fluoride, quinolate, or acetoacetate of an alkaline metal or an alkaline-earth metal

Methodology Applied

Scientific EffectElectron injection:

Implementation Method 2

a second material having a work function of about 2.6 to about 4.5 eV. The second material may include any one or more of ytterbium (Yb), aluminum (Al), silver (Ag), and magnesium (Mg)

Methodology Applied

Scientific EffectWork function:

Implementation Method 3

the anode may be manufactured by sputtering so as to reduce damage incurred during manufacture of large-area device

Methodology Applied

Scientific EffectSputtering: Sputtering

Implementation Method 4

light emission is achieved by energy released when excitons generated by combination of electrons and holes drop from the exited state to the ground state

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS8969864B2Organic light emitting device having a bulk layer comprising a first and second material

Publication Date: 2015.03.03 SAMSUNG DISPLAY CO LTD

AI summary

Disclosed is an organic light emitting diode device including an anode, a cathode, an emission layer between the anode and the cathode, and a buffer layer positioned between the emission layer and the anode. The buffer layer includes an oxide, fluoride, quinolate, or acetoacetate compound of an alkaline metal or an alkaline-earth metal, as well as a material having a work function of about 2.6 to about 4.5 eV. The buffer layer also has a thickness of about 30 Å to about 400 Å.